Ultra-thin body transistors such as FinFETs or Ultra-Thin Body and Box (UTBB) MOSFETs are required for sub-20 nm nodes because of their excellent electrostatic integrity and reduced variability. Compared to FinFET, UTBB technology on thin buried oxide presents two decisive benefits: a much simpler process than FinFET and the possibility to use the backplane bias to optimize the power consumption and speed trade-off at circuit level. To take full advantage of this latter benefit, circuit designers need compact models that describe properly the transistor behavior for a wide range of back bias.
S. Khandelwal, Y. S. Chauhan, D. D. Lu, S. Venugopalan, M. U. A. Karim, A. B. Sachid et al, “BSIM-IMG:A compact model for ultrathin-body SOI MOSFETs with back-gate control”, IEEE Transactions on Electron Devices, vol. 59, pp.2019-2026, 2012 and O. Rozeau, M. A. Jaud, T. Poiroux, M. Benosman, “Surface potential based model of ultra-thin fully depleted SOI MOSFET for IC simulations”, IEEE International SOI conference, 2011, have disclosed such compact models describing the transistor behavior. However, in such models, the interface between the body and the buried oxide is assumed always depleted, which provides correct results in reverse and low forward back bias (FBB) range. However, when a strong FBB is applied, inversion occurs first at the back interface, which has a significant impact on device characteristics. Consequently, the previous models are not realistic when a strong FBB is applied.